The present invention relates to phase change ink inkjet printers, and more particularly to the extension of the life of a drum maintenance unit used to deliver a release agent to a phase change ink inkjet printer transfer drum.
In solid phase change ink inkjet printers, where the ink is solid at room temperatures but is heated for ejection as a liquid onto an intermediate transfer surface, a drum maintenance unit is used as described in U.S. Pat. No. 5,805,191, incorporated herein by reference, to deliver a release agent, such as a silicone oil and/or functionalized oils, onto the intermediate transfer surface in order to allow an acceptable release of an image upon transfer from the intermediate transfer surface to media, such as paper or transparency. A certain amount of release agent is consumed for each simplex print so that the drum maintenance unit has to be replaced periodically when the release agent is fully consumed.
Currently the lifetime of the drum maintenance unit is specified according to a predetermined average release agent usage per print based upon a maximum customer usage profile, i.e., a usage profile that fits most customers. For example if the number of simplex prints specified for a particular drum maintenance unit is 30,000, then for each print the number is decremented in a memory or counter located in the drum maintenance unit until the number of copies reaches a low limit. At the low limit a message is provided on a display of the printer indicating to a user that the drum maintenance unit is in imminent need for replacement and a new unit should be ordered. When a very low limit is reached, the message produces an output indicating the remaining number of prints before the drum maintenance unit is depleted and needs to be replaced.
When the drum maintenance unit is replaced based upon the predetermined number of copies, there usually is still some release agent remaining in the drum maintenance unit reservoir that could be used to extend the life of the unit and produce more prints. Therefore what is desired is a scheme for extending the life of the drum maintenance unit by predicting more accurately the release agent usage without changing the hardware configuration of the drum maintenance unit.